We are testing the hypothesis that global gene expression profiling of the major trophoblast (TB) subpopulations of placentas from preeclampsia (PE) patients will lead to the identification of novel molecules that play important roles in this syndrome. The impetus for this strategy is the finding that PE is consistently associated with certain placental pathologies. The interstitial component of cytotrophoblast (CTB) invasion is frequently restricted to the superficial decidua. Likewise, endovascular invasion is constrained in terms of the number of spiral arterioles that are involved and the extent to which they are modified. Syncytiotrophoblasts (STBs) from placentas of affected patients also have overt changes such as syncytial knots. These alterations are accompanied by molecular changes, many of which have been identified by profiling, in PE, the expression of molecules that normally play important roles in terms of TB functions. However, we have begun to apply unbiased approaches to gain a more comprehensive understanding of changes in TB gene expression that occur in PE. This approach acknowledges our limited understanding of the placental component of this syndrome. Recently, we used a transcriptomics approach to profile CTB gene expression in various severe forms of PE (sPE). Specifically, CTBs that were isolated from the placentas of sPE patients and control women were cultured for 48 h to allow differentiation/invasion. Microarray analyses revealed sPE-associated upregulation of a suite of CTB genes that, by the end of the culture period, returned to control levels. They included factors previously associated with PE and many novel molecules, including the angiogenic regulator, SEMA3B. We went on to show that elevating levels of this neuropilin-1 and -2 ligand phenocopied many of the effects of PE on CTBs by mechanisms that include downregulating VEGF signaling through the PI3K/AKT and GSK3/ pathway. The same changes were observed in sPE CTBs. Our data support the theory that, in PE, the in vivo environment impairs CTB differentiation/invasion, the differentially expressed molecules contribute to the mechanisms, and that the clinical signs are determined by patient-specific factors. Having identified a genetic signature for invasive CTBs in sPE, we now propose an unbiased analysis of the three other affected TB populations, STBs, syncytial knots and endovascular CTBs. Specifically; we will use laser microdissection to isolate these cells from PE, sPE and control placentas and a global transcriptional profiling approach to identify the dysregulated genes (Aim 1). We will employ our new cell culture model, human TB progenitor cells, to determine the functional significance of the observed changes (Aim 2). We think that these experiments will yield new information about the molecular bases of placental defects in PE. The findings could also have significant translational potential, e.g., a subset of the dysregulated molecules could be circulating biomarkers and/or therapeutic targets for improving placental function, which our data suggest is possible.